Commit 7436ceb2 authored Feb 05, 2021 by NeilBrown Committed by Greg Kroah-Hartman Feb 23, 2021

net: fix iteration for sctp transport seq_files



commit af8085f3a4712c57d0dd415ad543bac85780375c upstream.

The sctp transport seq_file iterators take a reference to the transport
in the ->start and ->next functions and releases the reference in the
->show function.  The preferred handling for such resources is to
release them in the subsequent ->next or ->stop function call.

Since Commit 1f4aace6 ("fs/seq_file.c: simplify seq_file iteration
code and interface") there is no guarantee that ->show will be called
after ->next, so this function can now leak references.

So move the sctp_transport_put() call to ->next and ->stop.

Fixes: 1f4aace6 ("fs/seq_file.c: simplify seq_file iteration code and interface")
Reported-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 8c8bae3a

net/sctp/proc.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -230,6 +230,12 @@ static void sctp_transport_seq_stop(struct seq_file seq, void v)
		{
		struct sctp_ht_iter *iter = seq->private;

		if (v && v != SEQ_START_TOKEN) {
		struct sctp_transport *transport = v;

		sctp_transport_put(transport);
		}

		sctp_transport_walk_stop(&iter->hti);
		}

		@@ -237,6 +243,12 @@ static void sctp_transport_seq_next(struct seq_file seq, void v, loff_t pos)
		{
		struct sctp_ht_iter *iter = seq->private;

		if (v && v != SEQ_START_TOKEN) {
		struct sctp_transport *transport = v;

		sctp_transport_put(transport);
		}

		++*pos;

		return sctp_transport_get_next(seq_file_net(seq), &iter->hti);
		@@ -292,8 +304,6 @@ static int sctp_assocs_seq_show(struct seq_file seq, void v)
		sk->sk_rcvbuf);
		seq_printf(seq, "\n");

		sctp_transport_put(transport);

		return 0;
		}

		@@ -369,8 +379,6 @@ static int sctp_remaddr_seq_show(struct seq_file seq, void v)
		seq_printf(seq, "\n");
		}

		sctp_transport_put(transport);

		return 0;
		}